Significance of source and size in the mechanical response of human cerebral blood vessels

Monson, Kenneth L.; Goldsmith, Werner; Barbaro, Nicholas M.; Manley, Geoffrey T.

doi:10.1016/j.jbiomech.2004.05.004

Cited by 109 publications

(94 citation statements)

References 15 publications

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“…The reported diameter of the MCA varies from 2 to 4 mm (Monson et al, 2005;Serrador et al, 2000) and the average flow in the MCA is 2.6 mL/sec (van Osch et al, 2006). For reasons of symmetry, only the plane whose normal is parallel to the vessel axis needs to be considered in the simulations.…”

Section: Numerical Modelmentioning

confidence: 99%

Optimal Location for Arterial Input Function Measurements near the Middle Cerebral Artery in First-Pass Perfusion MRI

Bleeker

Buchem

Osch

2009

J Cereb Blood Flow Metab

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One of the main difficulties in obtaining quantitative perfusion values from dynamic susceptibility contrast-magnetic resonance imaging is a correct arterial input function (AIF) measurement, as partial volume effects can lead to an erroneous shape and amplitude of the AIF. Cerebral blood flow and volume scale linearly with the area under the AIF, but shape changes of the AIF can lead to large, nonlinear errors. Current manual and automated AIF selection procedures do not guarantee the exclusion of partial volume effects from AIF measurements. This study uses a numerical model, validated by phantom experiments, for predicting the optimal location for AIF measurements in the vicinity of the middle cerebral artery (MCA). Three different sequences were investigated and evaluated on a voxel-by-voxel basis by comparison with the ground truth. Subsequently, the predictions were evaluated in an in vivo example. The findings are fourfold: AIF measurements should be performed in voxels completely outside the artery, here a linear relation should be assumed between DR Ã 2 and the concentration contrast agent, the exact optimal location differs per acquisition type, and voxels including a small MCA yield also correct AIF measurements for segmented echo planar imaging when a short echo time was used.

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Section: Numerical Modelmentioning

confidence: 99%

Optimal Location for Arterial Input Function Measurements near the Middle Cerebral Artery in First-Pass Perfusion MRI

Bleeker

Buchem

Osch

2009

J Cereb Blood Flow Metab

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“…The radius of a middle cerebral artery is about 1.2 mm, which gives the estimation R 0 = 1.2 mm (Monson et al, 2005), and the thickness of a healthy adventitia is about H 0 = 30μm (Smith et al, 1981). The stiffness of the collagen fabric of the adventitia is accounted for by the factor n fb 0 β 0 μt cl = 3.3 MPa (Monson et al, 2005). In the collagen production law (Eq.…”

Section: Geometrical and Physical Parametersmentioning

confidence: 99%

“…Most bifurcations of the cerebral vasculature are structurally stable, but a small number develop a weakness that causes the wall to expand outwardly in the region near the flow divider of the branching artery (Austin et al, 1993;MacDonald et al, 2000;Rowe et al, 2003). Some measurements of the macroscopic mechanical properties of cerebral arteries and aneurysms exist (Coulson et al, 2004;Monson et al, 2003Monson et al, , 2005Scott et al, 1972;Steiger, 1990;Tóth et al, 1998Tóth et al, , 2005 and the structural organisation of these tissues is fairly well documented (Canham et al, 1991b(Canham et al, ,a, 1992(Canham et al, , 1996(Canham et al, , 1999Finlay et al, 1991Finlay et al, , 1995Finlay et al, , 1998Hassler, 1972;MacDonald et al, 2000;Rowe et al, 2003;Smith et al, 1981;Whittaker et al, 1988). In the aneurysmal wall, the tunica media and the internal elastic lamina have often disappeared or are severely fragmented (Abruzzo et al, 1998;Sakaki et al, 1997;Stehbens, 1963;Suzuki and Ohara, 1978;Tóth et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

Kroon

Holzapfel

2009

Journal of Theoretical Biology

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A new theoretical model for the growth of saccular cerebral aneurysms is proposed by extending the recent constitutive framework of Kroon and Holzapfel (J. Theor. Biol., 247:775-787, 2007). The continuous turnover of collagen is taken to be the driving mechanism in aneurysmal growth. The collagen production rate depends on the magnitude of the cyclic deformation of fibroblasts, caused by the pulsating blood pressure during the cardiac cycle. The volume density of fibroblasts in the aneurysmal tissue is taken to be constant throughout the growth process. The growth model is assessed by considering the inflation of an axisymmetric membranous piece of aneurysmal tissue, with material characteristics representative of a cerebral aneurysm. The diastolic and systolic states of the aneurysm are computed, together with its load-free state. It turns out that the value of collagen pre-stretch, that determines growth speed and stability of the aneurysm, is of pivotal importance. The model is able to predict aneurysms with typical berry-like shapes observed clinically, and the predicted wall stresses correlate well with the experimentally obtained ultimate stresses of this type of tissue. The model predicts that aneurysms should fail when reaching a size of about 1.2-3.6 mm, which is smaller than what has been clinically observed. With some refinements, the model may, however, be used to predict future growth of diagnosed aneurysms.

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“…The considered model geometry is according to a healthy human middle cerebral artery [96,97]: R 0 = 1.2 mm, H med = 0.25 mm, H adv = 0.30 µm. The size of the damage region, where the media is absent, is characterized by the radius R an set to be πR 0 /2.…”

Section: Model Specification Numericsmentioning

confidence: 99%

“…The size of the damage region, where the media is absent, is characterized by the radius R an set to be πR 0 /2. On the basis of investigations conducted by Monson et al [96], material stiffness parameters are set to µ M = 0.3 MPa and β 0 µ c t lf = 14 MPa (in [96] there is a substantial variation in results and the parameters chosen are from test specimens with a relatively low stiffness). The parameters k 1,med and k 2,med are based on material parameters for a carotid artery from a rabbit [98], for which k r 1,med = 2.3632 kPa, k r 2,med = 0.8393, µ r M = 3.0 kPa, where the superscript 'r' stands for 'rabbit'.…”

Section: Model Specification Numericsmentioning

confidence: 99%

Cardiovascular Mechanics

SpringerReference

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Modeling in biomechanics plays an important role in simulating biological functions and has great potential to aid medical clinicians in determining the cause of a disease, the type of treatment or by aiding in the training of a surgical procedure. Cardiovascular diseases (CVDs) are the leading cause of mortality today. This work therefore aims at developing a framework for modeling CVDs, such as cerebral aneurysms or heart diseases with increased myofiber dispersion as seen in, e.g., hypertrophic cardiomyopathy.To this end, a three-dimensional growth model of a human saccular cerebral aneurysm is presented that includes the anisotropy of the medial layer. It is shown that including fibers in the media reduces the maximum principal stress, thickness increase and shear stress in the aneurysm wall. It is also shown that the axial pre-stretch has a large impact on the stress levels and thickness increase in the aneurysm wall.In addition, the constituents needed for the numerical implementation of a structurally based constitutive law describing the behavior of passive myocardium is shown. A comparison is made between this invariant based model and a commonly used Green-Lagrange strain component based model and it is shown that using material parameters retrieved when both models is fitted using a simple shear mode experiment, the invariant based model is better suited to predict the stress in the myocardium for other modes of deformation. The passive cardiac model is coupled together with an evolution equation responsible for generating the active stress. A model of the left ventricle (LV) is presented where pressure is calculated as a response to the change in the ventricular volume in order to ensure physiologically realistic pressure-volume loops. The influence of myocardial fiber and sheet distribution is investigated by using two different setups, a generic setup and one based on experiments. The results implies that spatial heterogeneity may play a critical role in mechanical contraction of the LV and that geometrical descriptions of deformation are needed when evaluating the accuracy of a ventricular model.Further, a novel approach to model the dispersion of both the fiber and sheet orientations evident in, especially diseased, myocardium is presented. Analytical and numerical simulations show that the dispersion parameter has great effect on myocardial deformation and stress development. The results also show that the dispersion has a significant impact on pressure-volume loops of an LV, and in future simulations the presented dispersion model for myocardium may advantageously be used together with models of, e.g., growth and remodeling of various cardiac diseases. In cases where fiber-reinforced models are extended to include the effect of distributed fiber orientations, neither the mathematical nor physical motivation for tension-compression fiber switching is clear, and in fact several choices exist for the material modeler. Therefore, methods to study such switching mechanisms is explored by ana...

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Significance of source and size in the mechanical response of human cerebral blood vessels

Cited by 109 publications

References 15 publications

Optimal Location for Arterial Input Function Measurements near the Middle Cerebral Artery in First-Pass Perfusion MRI

Optimal Location for Arterial Input Function Measurements near the Middle Cerebral Artery in First-Pass Perfusion MRI

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

Cardiovascular Mechanics

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